Gilead Sciences (GILD) manufactures VIREAD--a very important HIV treatment. Check out the article below for another possibly even more lucrative use for viread. Another interesting piece of info re Gilead--they are the manufacturer of Tamiflu. Tamiflu is quite possibly the only effective current treatment against Bird Flu.
http://news.yahoo.com/s/ap/20060327/.../aids_new_hope
Summary: Viread has shown great promise in animal laboratory tests of actually PREVENTING HIV transmission.
Disclosure: I don't own any GILD shares. Always thoroughly research your stock picks before making the decision to invest.